Incidence of HIV has not decreased in 10 years and life expectancy continues to lag behind those who are uninfected despite tremendous advances in HIV care, including major improvements in effectiveness and availability of combination antiretroviral therapies (cART). Medication adherence is key to preventing HIV transmission and progression, yet only 28% of people living with HIV/AIDS (PLWHA) in the U.S. are using required medication routinely. While there are many factors that are associated with lower medication adherence, one of the most important barriers is alcohol use. Several studies have shown that alcohol use not only reduced medication adherence but also increased HIV transmission risk by unprotected and unplanned sex, and illicit drug use. With such high prevalence rates, reducing alcohol use to increase medication adherence is critical to lowering HIV transmission and progression. Previous studies lack details about an individual's intra- and inter-day alcohol use over time. Without those patterns of consumption and cART adherence, we are limited in our ability to effectively counsel patients about alcohol use and its effects on adherence and virologic outcomes. Our overall goal is to better understand the intra- and inter-day patterns of alcohol use that are detrimental to PLWHA in order to better inform future interventions to reduce alcohol use and increase medication adherence. Daily diary and ecological momentary assessment (EMA) studies provide a unique opportunity to examine in real time behavioral engagement and its predictors and consequences while utilizing naturalistic conditions and minimizing recall bias. This study aims to identify the critical details on patterns of use (type of alcohol, size of serving, number of servings, time of day, duration of use, and location consumed) that may enhance the design and effectiveness of future interventions aimed at reducing alcohol use and in turn, slowing HIV progression and reducing HIV transmission risk by improving cART adherence. The daily measurement of alcohol consumption, mood, and cART adherence has not been linked previously. With the rapidly growing population of smart phone owners, we propose that this technology offers a unique opportunity to better understand crucial aspects of detailed alcohol use patterns particularly related to daily medication adherence and pinpoint detrimental alcohol use patterns that will help inform intervention development for more effective real-world interventions aimed at reducing alcohol use and thereby transmission rates and slowing HIV progression. Specifically, our study aims to 1) collect detailed patterns of alcohol use based on: time of day when consumption begins, length of consumption, number of drinks consumed, type of alcohol, and location where consumption occurs, and 2) characterize the effect of detailed alcohol consumption on daily medication adherence among PLWHA (as measured by cART adherence, HIV viral load, CD4 cell count, liver functions). We hypothesize that certain patterns of alcohol consumption serve as determinants of poor health outcomes among PLHWA, through their impact on cART adherence patterns.